Sorry for the late reply, did you manage to get it to work or are you still facing this issue ?

Any good reason not to upgrade to macOS High-Sierra ? I found myself quite cautious in the past with macOS upgrades and the way they release versions without taking care of apps or plugins compatibility but since last year it tempt to be better, so I always do the updates now and have less issues ( I also take the time to see if there is warning from DAW or Plugins manufacturers before deciding to update ).

This one could be hard to troubleshoot, I have latest version of Kick 2 working fine here but I'am running macOS High-Sierra latest 10.13.6 (17G65) with latest Avid Pro Tools 2018.4.0

Is it crashing Pro Tools or just Kick 2 ? Does it happen just when you play your midi track or when doing something specific within Kick 2 GUI plugin ?